The present invention relates to an apparatus for seaming can ends to cylindrical cans which have been filled with contents.
One known can end seaming machine is disclosed in U.S. Pat. No. 1,929,339. A can after it has been filled with contents is delivered by a belt conveyor, then engaged by a disc-shaped feed turret, and a can end is placed on the can while the can is being turned and guided by the feed turret. Thereafter, the can is turned by a seaming turret while at the same time the can end and the can are seamed together under pressure by a seaming mechanism such as an arcuate seaming rail extending along the outer periphery of the clincher turret.
In the known can end seaming machine, when the turrets are rotated, the directions in which the cans are fed by these turrets vary at all times as they are guided along the arcuate paths. Therefore, the contents of the cans which are fed in the varying directions tend to be thrown out of the cans under centrifugal forces. When the cans are fed at higher speeds, it becomes more difficult to prevent the contents from being split from the cans. It has been possible to seam can ends to cans at a rate of 200 to 250 cans per minute, at most, while preventing the contents from being split from the cans.
The applicant has proposed a can end seaming apparatus which can seam can ends to cans at high speed while preventing filled contents from being split from of the cans (see Japanese Patent Application No. 63-141482).
The proposed can end seaming apparatus operates to seam can ends to cans while the cans, filled with contents, are being fed along a straight path.
As shown in FIG. 22 of the accompanying drawings, the proposed can end seaming apparatus has a first can feed means 100 for feeding cans X along a straight path, and a second can feed means 101 to which the cans X are transferred from the first can feed means 100, the second can feed means 101 being endless and movable along a substantially elliptical path, with one run extending parallel to the first can feed means 100.
As shown in FIG. 23, the second can feed means 101 has support tables 102 on which the cans X are rotatably supported. Can end holder means 103 for holding can ends Y are disposed upwardly of the support tables 102 in confronting relation thereto. The can end holder means 103 are associated with can end feed means 104 which feed the can ends Y that are held by the can end holder means 103. The can end feed means 104 and the support tables 102 are integrally joined to an endless chain 105, which is driven to feed the cans X and the can ends Y at the same time.
As illustrated in FIGS. 22 and 23, cans X which are transferred from the first can feed means 100 to the second can feed means 101 are fed by the second can feed means 101. While the cans X are being fed by the second can feed means 101, can ends Y which are supplied from a can end feeder C to the can end holder means 103 of the can end feed means 104 are lowered into covering relation to the openings of the cans X when the can end holder means 103 are moved downwardly by a lifting/lowering means (not shown).
As shown in FIG. 23, the can X and the can end Y which are sandwiched between the can end holder means 103 and the second can feed means 101 are rotated in unison by a rotative drive means so that the can X and the can end Y roll along a straight seaming means 106. The rotative drive means includes a pinion gear 107 on the outer periphery of each of the can end holder means 103, and a rack 108 meshing with the pinion gear 107 and extending in the can feeding direction along a seaming rail 109 which serves as a seaming means 106. When the second can feed means 101, which holds the can X covered with the can end Y, moves along the straight path, the can X is fed along the straight path while the can X is being rotated through the can end holder means 103 by the meshing engagement between the pinion gear 107 and the rack 108. During this time, the portions of the can X and the can end Y, which are to be seamed, are pressed by the seaming rail 109, so that the can end Y is seamed to the can X.
With the can end seaming apparatus thus constructed, the can end is seamed to the can while they are fed along the straight path at a constant speed. Since the direction in which the can X is fed remains unchanged, the contents of the can X are prevented from being split even if the can end Y is seamed at a higher seaming speed. Therefore, the canned products can be manufactured at a higher production rate.
However, various problems will arise if the seaming speed is increased for higher production efficiency.
The first problem is caused when the speed at which the cans are fed is increased for a higher can end seeming speed.
If the cans X are fed at an increased speed, when the second can feed means 101 which circulates along the endless elliptical path and the can end feed means 102 move arcuately and then enter the straight path along the seaming means 106, the pinion gear 107 and the rack 108 suddenly start meshing with each other. At this time, the teeth of the pinion gear 107 and the teeth of the rack 108 tend to be damaged. The faster the cans X are fed, the greater the damage to the teeth of the pinion gear 107 and the rack 108. When the teeth of the pinion gear 107 and the rack 108 are damaged, the can ends Y and the cans X cannot be rotated smoothly when they are to be seamed together, and hence the can ends Y and the cans X cannot reliably be seamed together.
In order to increase the speed at which the cans X are fed, it is necessary to separate the can end holder means 103 quickly from the can ends Y after the can ends Y have been seamed to the cans X.
Japanese Laid-Open Patent Publication No. 64-18538 shows a knockout pad disposed in a seaming chuck and movable vertically to separate the seaming chuck from a can end which has been seamed to a can. However, the disclosed arrangement is complex in structure, and cannot easily speed up the vertical movement of the knockout pad. If the vertical movement of the knockout pad is speeded up, then various parts of the can end seaming apparatus are worn soon, and hence the can end seaming apparatus becomes poor in durability.
The second problem is caused when the time required to seam a can end to a can is shortened for higher productivity. The shortened seaming time may be achieved by increasing the time required to feed the can and the can end, and also by reducing the time in which the portions of the can and the can end which are to be seamed together are being pressed against the seaming rail 109.
The portions of the can and the can end which are progressively held in rolling and pressed engagement with the straight seaming rail 109 are seamed to spirally different degrees along their outer peripheries. More specifically, these portions of the can and the can end are seamed to different degrees at starting and terminal ends of the seamed portions. The difference between the different seaming degrees is larger as the seaming rail 109 is shorter. The greater the diameter of the can end Y, the larger the difference between the different seaming degrees. The contents of the can may leak from the region where the can and the can end are seamed to a smaller degree. The region where the can and the can end are seamed to a larger degree tends to wrinkle or otherwise be distorted after they are seamed since the can and the can end are seamed rapidly in that region. It is therefore difficult to seam the can end Y to the can X highly uniformly and accurately along the entire circumference of the can end Y.
The third problem occurs when there are various cans with different heights and diameters. The production rate of the can end seaming apparatus cannot be increased unless it can easily cope with different types of cans to which corresponding can ends are to be seamed.
The second can feed means 101 of the disclosed can end seaming apparatus is of a substantially inverted C-shaped structure, as shown in FIG. 23, such that the distance between the can end holder means 103 and the tables 102 matches the height of the cans X to which the can ends Y are to be seamed. However, the second can feed means 101 cannot hold cans whose height does not match the distance between the can end holder means 103 and the support tables 102.
If cans of a different height are to be held by the second can feed means 101, then the blocks of the can end holder means 103 and the support tables 102, which were previously used to seam can ends to cans, need to be replaced with those blocks which lend themselves to the height of the cans of different height.
If cans of a different diameter are to be held by the second can feed means 101, then the can end holder means 103 have to be replaced with different can end holder means which match the diameter of those cans.
The above replacement processes are time-consuming and laborious, and hence lower the production rate of the can end seaming apparatus.